Conventional touch sensitive virtual buttons, i.e., buttons painted on a stationary flat surface and actuated by touch, are capacitance-based or resistance-based. Certain touch sensitive user input systems detect hovering objects as well. Examples include U.S. Publication No. 2008/0012835 A1 for HOVER AND TOUCH DETECTION FOR DIGITIZER and U.S. Publication No. 2006/0244733 A1 for TOUCH SENSITIVE DEVICE AND METHOD USING PRE-TOUCH INFORMATION.
Prior art hover detection systems based on reflected light determine a height of an object above a surface based on an amount of reflected light: the nearer the object—the more light is reflected onto the detector situated beneath the touch surface. Therefore, prior art systems are able to detect a hovering object over time and determine whether the object is moving closer or farther away based on relative amounts of detected light. I.e., diminishing light detection over time indicates an object moving away from the surface, and increasing light detection over time indicates an object moving toward the surface. In other words, the determined height is relative to other heights in a series of detections, but the actual height remains unknown. Indeed, different materials reflect different amounts of light, e.g., a white glove reflects more light than a black glove, and the reflective properties of a hovering object are not known by the system. Therefore, the system cannot determine the height at which the object is situated above the surface based on the amount of reflected light detected. In addition, because prior art proximity detectors require a series of detections of the object at different heights in order to rank the heights in relation to each other, a single proximity detection or a series of detections of a stationary hovering object will provide little information about the height of the object.
White goods typically have multiple controls that are set by a user. For example, a washing machine has controls for selecting the size of a wash load (e.g., large, medium, small), the fabric (e.g., cotton, synthetic, wool) and the temperature (e.g., hot, warm, cold). Some white goods have control panels having multiple touch-sensitive controls. In accordance with an embodiment of the present invention, white good control panels use light-based proximity sensors.
One problem with prior art proximity sensors is that they are prone to false touch detection, especially when the user wears shiny jewelry that reflects light onto a proximity sensor. For example, assume an array of controls placed together on a control panel, where a respective proximity sensor is situated underneath each control. When a user approaches or touches one control, a ring on the user's finger may reflect either ambient light, or light from one of the proximity sensors in the array, onto an unintended neighboring proximity sensor. This will erroneously activate the neighboring control. It would be advantageous to have a robust proximity sensor that distinguishes between intended touches and inadvertent reflections.